Active balance type high-resolution high-precision differential pressure gauge

Abstract

The invention relates to the technical field of differential pressure gauges, in particular to an active balance type high-resolution and high-precision differential pressure gauge. According to the technical scheme, the device comprises an internal pressure difference system for forming pressure difference in the device, an internal and external pressure difference comparison system, two inlet and outlet systems and a control system, and the control system controls the internal pressure difference system to work according to the balance state of the external pressure difference and the internal pressure difference. The internal pressure difference is adjusted through the pump, so that the external pressure difference and the internal pressure difference reach a balanced state, meanwhile, the control system records the accumulated revolution number of the pump, and the accumulated revolution number of the pump and the measured external pressure difference are in a linear relation and serve as the reading number of the measured pressure difference. The inlet and outlet system isolates an external measured fluid from an internal working fluid in the internal pressure difference system and the internal and external pressure difference comparison system. The differential pressure gauge has high precision and resolution, can resist high pressure, has little influence on the measurement precision by temperature change, and can greatly expand the application range of the differential pressure gauge.

Description

Technical Field

[0001] The invention relates to the technical field of differential pressure gauges, and in particular to an active balanced high-resolution and high-precision differential pressure gauge. Background Art

[0002] In modern industry, pressure differential measurement is required in many occasions. For example, the flow rate of fluid is measured by using ratio tubes, orifice plates and other measurement methods. Ratio tubes and orifice plates produce pressure differentials related to the flow rate. To collect this pressure differential information, a differential pressure meter is needed. The density and height of the fluid in certain containers can also be measured by measuring the pressure differential. Fluid height × fluid density × gravitational acceleration = pressure differential. After accurately measuring the pressure differential, the fluid density can be calculated if the fluid height is known, and the fluid height can be calculated if the fluid density is known.

[0003] At present, there are U-tube differential pressure gauges, diaphragm differential pressure gauges, etc. for measuring differential pressure. However, the performance needs to be improved. For example, the higher the resolution of the differential pressure measurement, the lower the static pressure resistance and the lower the measurement range. Some differential pressure gauges are sensitive to temperature, which affects the measurement accuracy. In addition, high-precision differential pressure gauges are more expensive. Summary of the invention

[0004] The purpose of the present invention is to provide an active balanced high-resolution and high-precision differential pressure gauge in view of the problems existing in the background technology.

[0005] The technical solution of the present invention is: an active balanced high-resolution and high-precision differential pressure gauge, comprising an internal differential pressure system for forming a pressure difference inside the device, an internal and external differential pressure comparison system, two inlet and outlet systems and a control system;

[0006] The high-pressure end of the internal pressure difference system is connected to one end of the internal-external pressure difference comparison system, the other end of the internal-external pressure difference comparison system is connected to the high-pressure end of the measured external pressure difference, the low-pressure end of the internal pressure difference system is connected to the low-pressure end of the measured external pressure difference, and the internal-external pressure difference comparison system detects whether the internal pressure difference is balanced with the external pressure difference;

[0007] The control system controls the operation of the internal pressure difference system according to the equilibrium state of the external pressure difference and the internal pressure difference, and adjusts the internal pressure difference so that the external pressure difference and the internal pressure difference reach an equilibrium state;

[0008] The inlet and outlet systems isolate the external measured fluid from the internal pressure difference system and the internal working fluid of the internal and external pressure difference comparison system.

[0009] Optionally, the internal and external pressure difference comparison system includes a liquid level comparison tube, a lower right liquid storage tube and an upper right liquid storage tube connected to the liquid level comparison tube, the upper right liquid storage tube is connected to a first pressure transmission tube, the first pressure transmission tube is provided with a high pressure end connected to the external pressure difference, the lower right liquid storage tube is connected to an internal pressure difference system, the upper right liquid storage tube is provided with a first perfusion system, an upper electrode and a lower electrode are installed in the upper right liquid storage tube, and a grounding electrode is installed on the lower right liquid storage tube.

[0010] Optionally, the inner diameter of the liquid level comparison tube is 6-16mm, and the length is 8-200mm. The inner diameters of the lower right liquid storage tube and the upper right liquid storage tube are both twice the inner diameter of the liquid level comparison tube. The length of the upper right liquid storage tube is half of the length of the liquid level comparison tube. The length of the lower right liquid storage tube is the same as that of the liquid level comparison tube. The liquid level comparison tube, the lower right liquid storage tube, the upper right liquid storage tube and the first pressure transmission tube are all made of insulating materials.

[0011] Optionally, the grounding electrode is inserted into the lower right liquid storage tube from the bottom, and the insertion height is the same as the height of the lower right liquid storage tube. A wiring length is left outside the lower right liquid storage tube for the grounding electrode, and the grounding electrode and the lower right liquid storage tube are sealed. The upper electrode and the lower electrode are inserted into the tube from the top of the upper right liquid storage tube, and the upper electrode is inserted into the middle position of the liquid level comparison tube. The insertion depth of the lower electrode is 1-4mm greater than that of the upper electrode. The distance between the upper electrode and the lower electrode and between them and the wall of the upper right liquid storage tube is greater than 2mm. A wiring length is left outside the upper right liquid storage tube for the upper electrode and the lower electrode, and the upper electrode and the lower electrode are sealed with the upper right liquid storage tube.

[0012] Optionally, the lower right liquid storage tube is filled with liquid level comparison tube heavy fluid, the lower right liquid storage tube is filled with fluid in the internal pressure difference system, the upper right liquid storage tube and the first pressure transmission tube are filled with liquid level comparison tube light fluid, the liquid level comparison tube heavy fluid and the fluid in the internal pressure difference system in the lower right liquid storage tube each occupy half the height, and the interface between the liquid level comparison tube heavy fluid and the liquid level comparison tube light fluid moves up and down within the range of the liquid level comparison tube as the external pressure difference changes.

[0013] Optionally, the internal pressure differential system includes a pressure differential tube connected to the internal pressure differential system, the pressure differential tube being respectively connected to a liquid storage tank and a second pressure transmission tube, the liquid storage tank being provided with a second perfusion system, the liquid storage tank being connected to a pump, the output end of the pump being provided with a first valve and a second valve, the input end of the pump being provided with a third valve and a fourth valve, the first valve being connected to the pressure differential tube, the second valve being connected to the liquid storage tank, the third valve being connected to the pressure differential tube, and the fourth valve being connected to the liquid storage tank.

[0014] Optionally, the inner diameter of the pressure differential tube is 0.002m-1m, the length of the pressure differential tube is 0.01m-20m, the fluid discharged by the pump per revolution is 0.01 ml / rev-10 ml / rev, the volume of the liquid storage tank is 1-1.2 times the volume of the pressure differential tube, the inner diameter of the second pressure transmission tube is 0.002m-0.04m, the lower part of the pressure differential tube is filled with internal pressure differential system heavy fluid, and the filling height is half of the height of the lower right liquid storage tube, the liquid storage tank is filled with internal pressure differential system heavy fluid, and the volume of the internal pressure differential system heavy fluid is the volume of the pressure differential tube minus the volume of the internal pressure differential system heavy fluid already filled in the pressure differential tube, the pressure differential tube, the liquid storage tank and the second pressure transmission tube are all in a connected state, and the remaining space among the pressure differential tube, the liquid storage tank and the pressure transmission tube is filled with internal pressure differential system light fluid.

[0015] Optionally, the control system controls the rotation and stop of the pump according to the conduction and disconnection signals of the upper electrode, the lower electrode and the ground electrode, and controls the opening and closing of the first valve, the second valve, the third valve and the fourth valve, and records the cumulative number of revolutions of the pump.

[0016] Optionally, the import and export system includes an internal fluid inlet and outlet of the device connected to the second pressure transmission tube and the high-pressure end connected to the external pressure difference, and also includes an import and export fluid isolation tube, an isolation soft capsule is installed in the import and export fluid isolation tube, the isolation soft capsule is connected to the internal fluid inlet and outlet of the device, the inlet and outlet of the measured fluid is installed on the inlet and outlet fluid isolation tube, the diameter of the inlet and outlet fluid isolation tube is 1-200mm, the volume of the inlet and outlet fluid isolation tube is twice the volume of the liquid level comparison tube, the wall thickness of the isolation soft capsule is between 0.1-5mm, the diameter of the isolation soft capsule is smaller than the inner diameter of the inlet and outlet fluid isolation tube, and the isolation soft capsule is elastic.

[0017] Optionally, the isolation soft capsule is filled with a liquid level comparison tube light fluid with a volume half of the liquid level comparison tube volume, the isolation soft capsule is filled with an internal pressure difference system light fluid with a volume half of the liquid level comparison tube volume, the rest of the inlet and outlet fluid isolation tube is filled with the measured fluid, and the measured fluid enters the inlet and outlet fluid isolation tube and presses the isolation soft capsule, the fluid in the isolation soft capsule enters the device, and the working fluid in the device enters the isolation soft capsule at the other end, the isolation soft capsule expands in volume, and the measured fluid is discharged out of the inlet and outlet fluid isolation tube on the other side.

[0018] In summary, the present application includes at least one of the following beneficial technical effects:

[0019] The device of the present invention uses a method of pumping fluid to actively form a pressure difference inside the device. The internal and external pressure difference comparison system detects whether the internal pressure difference is balanced with the external pressure difference. If it is detected that the high-pressure end pressure of the external pressure difference is greater than or less than the high-pressure end pressure of the internal pressure difference, the system sends a signal to the control system, and the control system drives the pump to work and adjust the internal pressure difference until the internal and external pressure difference comparison system reaches a balanced state. While driving the pump to work, the control system also records the cumulative number of revolutions of the pump. This cumulative number of revolutions is linearly related to the pressure difference of the external measured fluid, and the value of the pressure difference at each moment can be calculated. This differential pressure gauge has high precision and resolution, can withstand high pressure, and temperature changes have little effect on the measurement accuracy, which can greatly expand the application range of the differential pressure gauge. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Provide a structural schematic diagram of the present invention;

[0021] Figure 2 A schematic diagram of an internal and external pressure difference comparison system of the present invention;

[0022] Figure 3 is a schematic diagram of the internal pressure difference system of the present invention;

[0023] Figure 4 A schematic diagram of the internal pressure differential system of the present invention after adding multiple pressure differential tubes;

[0024] Figure 5 Schematic diagram of the import and export system of the present invention.

[0025] Reference numerals: 101, internal pressure difference system; 102, internal and external pressure difference comparison system; 103, inlet and outlet system; 201, liquid level comparison tube; 202, lower right liquid storage tube; 203, upper right liquid storage tube; 204, first pressure transmission tube; 205, grounding electrode; 206, upper electrode; 207, lower electrode; 208, heavy fluid in liquid level comparison tube; 209, light fluid in liquid level comparison tube; 210, fluid in internal pressure difference system; 211, connected to external pressure difference high pressure end; 212, connected to internal pressure difference system; 213, first perfusion system; 30 1. Liquid storage tank; 302. Pressure differential tube; 303. First valve; 304. Second valve; 305. Third valve; 306. Fourth valve; 307. Pump; 308. Second perfusion system; 309. Light fluid of internal pressure differential system; 310. Heavy fluid of internal pressure differential system; 311. Second pressure transmission tube; 401. U-shaped pressure differential tube; 501. Inlet and outlet fluid isolation tube; 502. Isolation soft capsule; 503. Inlet and outlet of internal fluid of device; 504. Inlet and outlet of measured fluid; 505. Measured fluid; 506. Fluid in device. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0027] Examples, such as Figures 1 to 5 As shown, an active balanced high-resolution and high-precision differential pressure gauge proposed by the present invention includes an internal differential pressure system 101, an internal and external differential pressure comparison system 102, two inlet and outlet systems 103 and a control system. The liquid level comparison tube 201 has an inner diameter of 8 mm and a length of 50 mm, the lower right liquid storage tube 202 has an inner diameter of 16 mm and a length of 50 mm, the upper right liquid storage tube 203 has an inner diameter of 16 mm and a length of 25 mm, and the inner diameter of the first pressure transmission tube 204 can be smaller, and a tube with an inner diameter of 8 to 12 mm can be selected. Each electrode has a diameter of 1 mm, and a tungsten-copper alloy electrode can be selected. The grounding electrode 205 is inserted into the lower right liquid storage tube 202 from the bottom, with an insertion depth of 50 mm, and is located in the center of the lower right liquid storage tube 202, and a sufficient wiring length is reserved outside the lower right liquid storage tube 202, and the grounding electrode 205 is sealed with the bottom plate of the lower right liquid storage tube 202. The upper electrode 206 and the lower electrode 207 are inserted into the upper right liquid storage tube 203 from the top, the two electrodes are 2 mm apart, and are located in the center of the upper right liquid storage tube 203. The lower end of the upper electrode 206 is located in the middle of the liquid level comparison tube 201, and the lower end of the lower electrode 207 is 4 mm below the lower end of the upper electrode 206. Sufficient wiring length is left for the upper electrode 206 and the lower electrode 207 outside the liquid level comparison tube 201, and the upper electrode 206 and the lower electrode 207 are sealed with the upper plate of the upper right liquid storage tube 203.

[0028] Further, in the internal pressure difference system, the pressure difference pipe 302 selects a pipe with an inner diameter of 16 mm and a length of 1 meter, and the liquid storage tank 301 selects a pipe with an inner diameter of 16 mm and a length of 1.1 meters. The first valve 303, the second valve 304, the third valve 305, and the fourth valve 306 all use valves and connecting pipelines with a diameter of 4 to 8 mm. The pump 307 selects a positive displacement pump with a displacement of 0.03 to 0.06 ml per revolution, and the inlet and outlet pipelines of the pump are connected to the valve pipeline through a reducer. The inner diameter of the second pressure transmission pipe 311 can be smaller, and a pipe with an inner diameter of 8 to 16 mm can be selected. Other pipelines of the system can use pipes with an inner diameter of 8 to 12 mm.

[0029] Furthermore, the inlet and outlet fluid isolation tube 501 has an inner diameter of 15 mm and a length of 60 mm, the isolation soft capsule 502 has a diameter of 8 mm and a length of 50 mm, and the isolation soft capsule 502 and the outlet pipe need to be tightened and sealed.

[0030] Device fluid perfusion method:

[0031] Import and export system filling:

[0032] (1) Open the inlet and outlet valves, and inject the measured fluid 505 from the inlet and outlet of the measured fluid until the inlet and outlet fluid isolation tube 501 is filled with the measured fluid 505 and the isolation soft capsule 502 is compressed. The inlet and outlet systems in both directions are the same;

[0033] (2) The inlet and outlet system in the inlet direction injects 2.5 ml of the liquid level comparison tube light fluid 209 from the internal fluid inlet and outlet 503 of the device into the isolation soft capsule 502, and the inlet and outlet system in the outlet direction injects 2.5 ml of the internal pressure difference system heavy fluid 310 from the internal fluid inlet and outlet 503 of the device into the isolation soft capsule 502;

[0034] (3) Close the valves of the fluid inlet and outlet 503 inside the device and the inlet and outlet of the measured fluid. During the fluid filling process, be sure to remove all air from each part.

[0035] Internal and external pressure difference comparison system filling:

[0036] (1) Connect the already filled inlet and outlet systems to the internal and external pressure difference comparison system;

[0037] (2) Open the valve connected to the external pressure differential high pressure end 211, and close the valve connected to the internal pressure differential system 212;

[0038] (3) The internal pressure difference system heavy fluid 310 is perfused from the valve of the first perfusion system 213 at the upper part of the upper right liquid storage pipe 203 to the lower right liquid storage pipe 202, and the perfusion height is half of the height of the lower right liquid storage pipe 202;

[0039] (4) Filling the liquid level comparison tube heavy fluid 208 into the lower right liquid storage tube 202, the filling height being half of the liquid level comparison tube 201;

[0040] (5) Infuse the liquid level comparison tube light fluid 209 into the upper right liquid storage tube 203 until the liquid level exceeds the first pressure transmission tube 204, continue to infuse and open the valve of the first infusing system 213 on the upper part of the first pressure transmission tube 204, and the liquid level comparison tube light fluid 209 enters the first pressure transmission tube 204. The infusing flow rate must be small to ensure that the original air in the tube is discharged from the upper part. When the liquid level comparison tube light fluid 209 fills the first pressure transmission tube 204 and the upper right liquid storage tube 203, close the two valves of the first infusing system 213. During the infusing process, the air in each part must be completely removed.

[0041] Internal pressure differential system filling:

[0042] (1) Connect the internal pressure difference system to the already filled internal and external pressure difference comparison system and the inlet and outlet systems. Close the connected valves;

[0043] (2) Calculate the total amount of fluid contained in the pipeline connected to the pump valve group. Open all valves of the pump valve group;

[0044] (3) The valve of the second perfusion system 308 on the pressure differential tube 302 is opened and connected to a vacuum pump. The valve of the second perfusion system 308 on the liquid storage tank 301 is closed and connected to an open container. The container is filled with an internal pressure differential system heavy fluid 310, the amount of which is 200 ml (the volume of the pressure differential tube 302) plus the total amount of fluid contained in the pipeline connected to the valve group. The valve of the second perfusion system 308 on the second pressure transmission tube 311 is closed;

[0045] (4) Vacuuming;

[0046] (5) Close the valve connected to the vacuum pump and open the valve connected to the open container. The internal pressure differential system heavy fluid 310 in the open container flows into the liquid storage tank 301 and the bottom of the pressure differential pipe 302. All connecting pipelines of the pump valve group are filled with the internal pressure differential system heavy fluid 310.

[0047] (6) Open the valve connected to the vacuum pump, remove the vacuum pump, and pour the internal pressure difference system light fluid 309 into the liquid storage tank 301 and the pressure difference tube 302 through the open container until the liquid level exceeds the second pressure transmission tube 311, and continue to pour. At the same time, open the valve of the second pouring system 308 on the upper part of the second pressure transmission tube 311, and the internal pressure difference system light fluid 309 enters the second pressure transmission tube 311. The pouring flow rate must be small to ensure that the original air in the tube is discharged from the upper part. When the internal pressure difference system light fluid 309 fills the second pressure transmission tube 311 and the liquid storage tank 301 and the upper part of the pressure difference tube 302, close all the valves of the second pouring system 308. During the pouring process, the air in each part must be completely removed. The working fluid can be selected according to the specific measurement situation, such as using low-viscosity silicone oil as the liquid level comparison tube light fluid 209, using salt water as the liquid level comparison tube heavy fluid 208, using water as the internal pressure difference system light fluid 309, and using carbon tetrachloride as the internal pressure difference system heavy fluid 310.

[0048] In this embodiment, it also includes a control system, which controls the rotation and stop of the pump 307 according to the conduction and disconnection signals of the upper electrode 206, the lower electrode 207 and the ground electrode 205, controls the opening and closing of the first valve 303, the second valve 304, the third valve 305 and the fourth valve 306, and records the cumulative number of revolutions of the pump 307.

[0049] Specifically, when the external pressure difference is static and unchanged, the heavy fluid 208 in the liquid level comparison tube 201 of the internal and external pressure difference comparison system 102 just touches the lower electrode 207, and the lower electrode 207 and the ground electrode 205 conduct current. The control system controls the pump 307 to stop rotating, the first valve 303 and the fourth valve 306 are opened, and the second valve 304 and the third valve 305 are closed. This state is the reference point for measuring the pressure difference. When the external pressure difference increases to a value greater than the internal pressure difference, the light fluid 209 in the level comparison tube 201 floods the lower electrode 207, the current between the lower electrode 207 and the ground electrode 205 is interrupted, and the control system drives the pump 307 to rotate. At this time, the heavy fluid 310 in the internal pressure difference system in the liquid storage tank 301 flows into the pressure difference tube 302, and the internal pressure difference increases, causing the contact interface between the two fluids in the level comparison tube 201 to move upward until the heavy fluid 208 in the level comparison tube just contacts the lower electrode 207. The control system controls the pump 307 to stop rotating and return to the reference state. The number of revolutions of the pump 307 between the two reference states is linearly related to the change in the external pressure difference during this period. Therefore, the cumulative number of revolutions of the pump 307 at a certain moment is linearly related to the increase in the external pressure difference from 0 to this moment.

[0050] Furthermore, if the changes in the external pressure difference are all upward changes, the external pressure difference can be measured by the above method. However, if the external pressure difference changes downward, another method must be used for measurement. When the external pressure difference decreases, the two fluid contact interfaces in the liquid level comparison tube 201 move upward. When the heavy fluid 208 in the liquid level comparison tube contacts the upper electrode 206, current is conducted between the upper electrode 206 and the ground electrode 205. After the control system receives this signal, it first controls the first valve 303, the second valve 304, the third valve 305 and the fourth valve 306 in the internal pressure difference system, the first valve 303 and the fourth valve 306 are closed, the second valve 304 and the third valve 305 are opened, and at the same time, the revolution recording method is changed from adding up the revolutions to subtracting the revolutions (i.e., one revolution of the pump 307 is subtracted from the accumulated revolutions), and then the pump 307 is driven to rotate. At this time, the internal pressure difference system heavy fluid 310 in the pressure difference tube 302 flows into the liquid storage tank 301, and the internal pressure difference is reduced, causing the two fluid contact interfaces in the liquid level comparison tube 201 to move downward until the liquid level comparison tube heavy fluid 208 just breaks away from the upper electrode 206, and the current between the upper electrode 206 and the ground electrode 205 is interrupted. After receiving this signal, the control system starts the delay system to keep the current state for a period of time. The delay time is related to the specific device size. The delay requires the two fluid contact interfaces in the liquid level comparison tube 201 to continue to move downward until the liquid level comparison tube light fluid 209 submerges the lower electrode 207, with a submergence depth of 1 to 20 mm. After the delay ends, the control system controls the valve group (first valve 303, second valve 304, third valve 305, fourth valve 306) in the internal pressure difference system and the revolution recording mode to change, the first valve 303 and the fourth valve 306 are opened, the second valve 304 and the third valve 305 are closed, and the revolution recording mode is changed from cumulatively decreasing the revolutions to cumulatively increasing the revolutions, and the pump 307 continues to rotate. At this time, the heavy fluid 310 of the internal pressure difference system in the liquid storage tank 301 flows into the pressure difference tube 302, and the internal pressure difference increases, so that the contact interface of the two fluids in the liquid level comparison tube 201 moves upward until the heavy fluid 208 of the liquid level comparison tube just contacts the lower electrode 207, and the control system controls the pump 307 to stop rotating and return to the reference state. After the above operation when the external pressure difference decreases, it can be ensured that the revolutions are accumulated in the reference state to ensure accuracy.

[0051] In order to increase the range of differential pressure measurement, the internal differential pressure system 101 can be connected in series when necessary, such as Figure 4As shown, the difference from the structure of a single pressure differential tube 302 is that multiple U-shaped pressure differential tubes 401 are connected in series between the original pressure differential tube 302 and the liquid storage tank 301. In the figure, two U-shaped pressure differential tubes 401 are connected in series (4 pressure differential tubes 302). During filling, the original pressure differential tube 302 and the liquid storage tank 301 are filled in the same way. Each U-shaped pressure differential tube 401 connected in series is filled with half the height of the internal pressure differential system heavy fluid, and the remaining part is filled with the internal pressure differential system light fluid 309.

[0052] It should be noted that when the external pressure difference decreases slightly, the upward movement of the two fluid interfaces in the liquid level comparison tube 201 is relatively small, and the heavy fluid 208 in the liquid level comparison tube does not contact the upper electrode 206. In this way, the control system does not receive any signal, and the pump 307 does not act. In order to accurately measure, a timed patrol mode can be adopted. If the control system does not receive any signal within a certain period of time, it can drive the delay system, first control the valve group in the internal pressure difference system to change, the first valve 303 and the fourth valve 306 are closed, the second valve 304 and the third valve 305 are opened, and at the same time change the revolution recording method from adding up the revolutions to subtracting the revolutions (i.e., one revolution of the pump 307 is subtracted from the accumulated revolutions), and then drive the pump 307 to rotate. At this time, the heavy fluid 310 of the internal pressure difference system in the pressure difference tube 302 flows into the liquid storage tank 301, the internal pressure difference decreases, and the contact interface of the two fluids in the liquid level comparison tube 201 moves downward. After the delay ends, the light fluid 209 in the liquid level comparison tube submerges the lower electrode 207. At this time, the control system controls the valve group and the revolution recording mode in the internal pressure difference system to change, the first valve 303 and the fourth valve 306 are opened, the second valve 304 and the third valve 305 are closed, and the revolution recording mode is changed from cumulative revolution to cumulative revolution. The pump 307 continues to rotate, and the contact interface between the two fluids moves upward until the liquid level comparison tube heavy fluid 208 just contacts the lower electrode 207. The control system controls the pump 307 to stop rotating and return to the reference state. This operation can accurately measure the small reduction in the external pressure difference.

[0053] Determine the zero point of differential pressure measurement. When all systems are connected and all systems are filled, the next step is to determine the zero point of differential pressure. In addition, the zero point must be determined after the device has been used for a period of time or the working state has changed. The method is to connect the inlet and outlet of the device and connect them to the low-pressure end of the external pressure difference. At this time, there may be three situations. The first is that the liquid level is relatively light and the fluid 209 floods the lower electrode 207. At this time, the control system drives the pump 307 to work according to the mode that the external pressure difference is greater than the internal pressure difference. After reaching the reference state, the pump 307 stops, and the cumulative number of revolutions of the pump 307 has a value. At this time, the cumulative number of revolutions is cleared to correspond to the zero point of the external pressure difference. The second is that the liquid level is relatively heavy and the fluid 208 floods the upper electrode 206. At this time, the control system drives the pump 307 to work according to the mode that the external pressure difference is less than the internal pressure difference. After reaching the reference state, the pump 307 stops, and the cumulative number of revolutions of the pump 307 has a value. At this time, the cumulative number of revolutions is cleared to correspond to the zero point of the external pressure difference. The third type is that the liquid level comparison tube heavy fluid 208 only submerges the lower electrode 207. At this time, the control system drives the pump 307 to work according to the timed patrol mode. After reaching the reference state, the pump 307 stops. The accumulated revolutions of the pump 307 have a value. At this time, the accumulated revolutions are cleared to correspond to the zero point of the external pressure difference. After that, the inlet of the device is connected to the high pressure end of the external pressure difference, and the outlet is connected to the low pressure end of the external pressure difference, and normal measurement begins.

[0054] In this embodiment, before the formal operation, the isolation soft capsule 502 of the inlet system is pre-injected with the liquid level comparison tube light fluid 209 of half the volume of the liquid level comparison tube 201, and the isolation soft capsule 502 of the outlet system is pre-injected with the internal pressure difference system light fluid 309 of half the volume of the liquid level comparison tube 201, and the rest of the inlet and outlet fluid isolation tube 501 is filled with the measured fluid. During operation, the measured fluid entering the inlet and outlet fluid isolation tube 501 squeezes the liquid level comparison tube light fluid 209 in the isolation soft capsule 502 and enters the internal and external pressure difference comparison system 102, the inlet and outlet system 103 has the internal pressure difference system light fluid 309 entering the isolation soft capsule 502 to expand its volume, and the inlet and outlet fluid isolation tube 501 has the measured fluid 505 flowing out, forming the flow of the entire system. When the volume of the measured fluid 505 entering the inlet and outlet fluid isolation tube 501 is greater than the volume of the fluid pre-injected in the isolation soft capsule 502, the isolation soft capsule 502 is flattened, and more measured fluid cannot enter the inlet and outlet system 103. After that, the internal pressure difference system works to balance the internal and external pressure differences, the light fluid 209 in the liquid level comparison tube returns to the isolation soft capsule 502, and the inlet and outlet system 103 returns to the state at the beginning of work.

[0055] Working principle: The internal and external pressure difference comparison system 102 is filled with the conductive level comparison tube heavy fluid 208 and the insulating level comparison tube light fluid 209. The internal and external pressure difference comparison system 102 determines which is greater between the external pressure difference and the internal pressure difference by the position of the contact liquid surface of the conductive level comparison tube heavy fluid 208 and the insulating level comparison tube light fluid 209 in the level comparison tube 201. The smaller the density difference between the two, the greater the displacement of the contact liquid surface when the pressure difference changes, and the higher the sensitivity of the internal and external pressure difference comparison system. However, the level comparison tube heavy fluid 208 and the level comparison tube light fluid 209 are not miscible and cannot form adhesion with the inner wall of the selected tube.

[0056] For the internal pressure difference system, the larger the diameter of the pressure difference tube, the less fluid is discharged per revolution of the pump 307, the smaller the density difference between the light fluid 309 of the internal pressure difference system and the heavy fluid 310 of the internal pressure difference system, and the higher the resolution and accuracy of the measurement. Due to the above factors, under the same pressure difference change, the pump needs to rotate more times to balance the internal and external pressure differences, thereby increasing the resolution and accuracy. The longer the pressure difference tube, the greater the density difference between the light fluid 309 of the internal pressure difference system and the heavy fluid 310 of the internal pressure difference system, and a larger internal pressure difference can be formed to balance the external pressure difference, thereby expanding the range. If high precision and high resolution are pursued, the measurement will be slow, the measurement time will be increased, and the range will be reduced. Therefore, the size design of the pressure difference tube 302 and the selection of the light fluid 309 of the internal pressure difference system and the heavy fluid 310 of the internal pressure difference system need to be specifically designed according to actual requirements.

[0057] The above specific embodiments are only several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant inspirations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. An active balanced high-resolution and high-precision differential pressure gauge, characterized in that: It includes an internal pressure difference system (101) for forming a pressure difference inside the device, an internal and external pressure difference comparison system (102), two inlet and outlet systems (103) and a control system; The high-pressure end of the internal pressure difference system (101) is connected to one end of the internal-external pressure difference comparison system (102), the other end of the internal-external pressure difference comparison system (102) is connected to the high-pressure end of the external pressure difference to be measured, the low-pressure end of the internal pressure difference system (101) is connected to the low-pressure end of the external pressure difference to be measured, and the internal-external pressure difference comparison system (102) detects whether the internal pressure difference is balanced with the external pressure difference; The control system controls the operation of the internal pressure difference system (101) according to the equilibrium state of the external pressure difference and the internal pressure difference, and adjusts the internal pressure difference so that the external pressure difference and the internal pressure difference reach an equilibrium state; The inlet and outlet system (103) isolates the external measured fluid from the internal pressure difference system (101) and the internal working fluid of the internal and external pressure difference comparison system (102).

2. The active balanced high-resolution and high-precision differential pressure gauge according to claim 1, characterized in that: The internal and external pressure difference comparison system (102) comprises a liquid level comparison tube (201), a lower right liquid storage tube (202) and an upper right liquid storage tube (203) connected to the liquid level comparison tube (201); the upper right liquid storage tube (203) is connected to a first pressure transmission tube (204); the first pressure transmission tube (204) is provided with a high pressure end (211) connected to an external pressure difference; the lower right liquid storage tube (202) is connected to an internal pressure difference system (212); the upper right liquid storage tube (203) is provided with a first perfusion system (213); an upper electrode (206) and a lower electrode (207) are installed in the upper right liquid storage tube (203); and a grounding electrode (205) is installed on the lower right liquid storage tube (202).

3. The active balanced high-resolution and high-precision differential pressure gauge according to claim 2, characterized in that: The inner diameter of the liquid level comparison tube (201) is 6 mm to 16 mm, and the length is 8 mm to 200 mm. The inner diameters of the lower right liquid storage tube (202) and the upper right liquid storage tube (203) are both twice the inner diameter of the liquid level comparison tube (201). The length of the upper right liquid storage tube (203) is half the length of the liquid level comparison tube (201). The length of the lower right liquid storage tube (202) is the same as that of the liquid level comparison tube (201). The liquid level comparison tube (201), the lower right liquid storage tube (202), the upper right liquid storage tube (203) and the first pressure transmission tube (204) are all made of insulating materials.

4. The active balanced high-resolution and high-precision differential pressure gauge according to claim 3, characterized in that: The grounding electrode (205) is inserted into the lower right liquid storage tube (202) from the bottom thereof, and the insertion height is the same as the height of the lower right liquid storage tube (202). The grounding electrode (205) leaves a wiring length outside the lower right liquid storage tube (202). The grounding electrode (205) and the lower right liquid storage tube (202) are sealed. The upper electrode (206) and the lower electrode (207) are inserted into the upper right liquid storage tube (203) from the top thereof. The upper electrode (206) is inserted into the liquid level comparison tube (201). ), the lower electrode (207) is inserted 1 mm to 4 mm deeper than the upper electrode (206), the distance between the upper electrode (206) and the lower electrode (207) and the wall of the upper right liquid storage tube (203) is greater than 2 mm, the upper electrode (206) and the lower electrode (207) are both provided with a wiring length outside the upper right liquid storage tube (203), and the upper electrode (206) and the lower electrode (207) are sealed with the upper right liquid storage tube (203).

5. The active balanced high-resolution and high-precision differential pressure gauge according to claim 4, characterized in that: The lower right liquid storage tube (202) is filled with a liquid level comparison tube heavy fluid (208), the lower right liquid storage tube (202) is filled with an internal pressure difference system fluid (210), the upper right liquid storage tube (203) and the first pressure transmission tube (204) are filled with a liquid level comparison tube light fluid (209), the liquid level comparison tube heavy fluid (208) and the internal pressure difference system fluid (210) in the lower right liquid storage tube (202) each occupy half the height, and the interface between the liquid level comparison tube heavy fluid (208) and the liquid level comparison tube light fluid (209) moves up and down within the range of the liquid level comparison tube (201) as the external pressure difference changes.

6. The active balanced high-resolution and high-precision differential pressure gauge according to claim 5, characterized in that: The internal pressure differential system comprises a pressure differential tube (302) connected to the internal pressure differential system (212); the pressure differential tube (302) is respectively connected to a liquid storage tank (301) and a second pressure transmission tube (311); the liquid storage tank (301) is provided with a second perfusion system (308); the liquid storage tank (301) is connected to a pump (307); the output end of the pump (307) is provided with a first valve (303) and a second valve (304); the input end of the pump (307) is provided with a third valve (305) and a fourth valve (306); the first valve (303) is in communication with the pressure differential tube (302); the second valve (304) is in communication with the liquid storage tank (301); the third valve (305) is in communication with the pressure differential tube (302); and the fourth valve (306) is in communication with the liquid storage tank (301).

7. The active balanced high-resolution and high-precision differential pressure gauge according to claim 6, characterized in that: The inner diameter of the pressure differential tube (302) is 0.002m-1m, the length of the pressure differential tube (302) is 0.01m-20m, the fluid discharged by the pump (307) is 0.01ml / rev-10ml / rev per revolution, the volume of the liquid storage tank (301) is 1-1.2 times the volume of the pressure differential tube (302), the inner diameter of the second pressure transmission tube (311) is 0.002m-0.04m, the bottom of the pressure differential tube (302) is filled with the internal pressure differential system heavy fluid (310), and the filling height is at the lower right storage tank. The liquid storage tank (301) is filled with the heavy fluid (310) of the internal pressure difference system, and the volume is the volume of the pressure difference tube (302) minus the volume of the heavy fluid (310) of the internal pressure difference system that has been filled in the pressure difference tube (302). The pressure difference tube (302), the liquid storage tank (301) and the second pressure transmission tube (311) are all in a connected state, and the remaining space among the pressure difference tube (302), the liquid storage tank (301) and the second pressure transmission tube (311) is filled with the light fluid (309) of the internal pressure difference system.

8. The active balanced high-resolution and high-precision differential pressure gauge according to claim 7, characterized in that: The control system controls the rotation and stop of the pump (307) according to the on and off signals of the upper electrode (206), the lower electrode (207) and the ground electrode (205), and controls the opening and closing of the first valve (303), the second valve (304), the third valve (305) and the fourth valve (306), and records the accumulated number of revolutions of the pump (307).

9. The active balanced high-resolution and high-precision differential pressure gauge according to claim 8, characterized in that: The inlet and outlet system (103) comprises an inlet and outlet (503) of the device internal fluid connected to the second pressure transmission tube (311) and the high pressure end (211) connected to the external pressure difference, and also comprises an inlet and outlet fluid isolation tube (501), an isolation soft capsule (502) is installed in the inlet and outlet fluid isolation tube (501), the isolation soft capsule (502) is connected to the inlet and outlet (503) of the device internal fluid, and a measured fluid inlet and outlet (504) is installed on the inlet and outlet fluid isolation tube (501). The diameter of the inlet and outlet fluid isolation tube (501) is 1 mm-200 mm, and the volume of the inlet and outlet fluid isolation tube (501) is twice the volume of the liquid level comparison tube (201). The wall thickness of the isolation soft capsule (502) is between 0.1 mm and 5 mm, and the diameter of the isolation soft capsule (502) is smaller than the inner diameter of the inlet and outlet fluid isolation tube (501), and the isolation soft capsule (502) is elastic.

10. The active balanced high-resolution and high-precision differential pressure gauge according to claim 9, characterized in that The isolation soft capsule (502) is filled with a liquid level comparison tube light fluid (209) with a volume half that of the liquid level comparison tube (201), and the isolation soft capsule (502) is filled with an internal pressure difference system light fluid (309) with a volume half that of the liquid level comparison tube (201). The rest of the inlet and outlet fluid isolation tube (501) is filled with the measured fluid (505). After the measured fluid (505) enters the inlet and outlet fluid isolation tube (501), it presses the isolation soft capsule (502). The fluid in the isolation soft capsule (502) enters the device. The working fluid in the device enters the isolation soft capsule (502) at the other end. The volume of the isolation soft capsule (502) expands, and the measured fluid (505) is discharged out of the inlet and outlet fluid isolation tube (501) on the other side.

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